Foreign particles occurring during fabrication process of LSIs, flat panel displays or solar panels often cause a reduction of yield and/or availability of the fabrication device. A high cleanness is requested in the fabrication device of LSIs, flat panel displays or solar panels because the foreign particles often deposit on substrates of wafers or glasses, and so on.
Practically, major foreign particles occur in a surface structuring device such as a plasma-etching device or a film forming device such as a sputtering device or a CVD device. The foreign particles are considered to be a main cause to reduce the yield and/or availability of the fabrication devices by depositing on the substrates (Non-patent Documents 1, 3). In addition the foreign particles sometimes play a role of mask during exposure, surface structuring or film forming processes. As a result, the foreign particles may cause circuit pattern defects even after removal of the foreign particles by cleaning of the substrates and reduce the yields or quality of the products.
The numbers of foreign particles are observed using a monitoring substrate in a mass production lines, and when the number exceeds a predetermined value, insides of the manufacturing devices are cleaned. However, it is difficult to clean the devices frequently because it takes much time and costs and therefore it reduces the availability of the devices.
A dry etching apparatus to process a surface of a substrate is a processing device that generates deposition of foreign particles during a surface structuring. Semiconductor wafers to be processed are introduced in an evacuated chamber by a transporting device. A securing device using electrostatic force, for example is provided in the evacuated chamber. An evacuation device is connected with the evacuated chamber and the chamber is maintained in negative (vacuum) pressure. A process gas is introduced in the chamber by a gas introducing device and an etching energy is supplied by a reaction energy supplying device and then the chamber is served as a dry-etching device to process the surface of the substrates.
A part of reaction products produced during the surface structuring of the wafers is discharged by the evacuation device or taken out with the substrates; however, the remainder is accumulated in the chamber. Generally, the inside of the chamber becomes dirty, that is, the amount of deposits is increased depending on the quantity of the substrates processed in the chamber. Therefore, the accumulated foreign particles inside the chamber should be removed (cleaned) and then a new process cycle (period) is started.
A method to judge and treat an error data by feedback control system is disclosed in Patent Document 1
In Patent Document 2, it is described that there is no proportional relation between the amount of deposits and foreign particles deposited on the substrates and the foreign particles has a tendency to increase when the amount of deposit exceeds some threshold value.
It is pointed out in Patent Document 3 there is a tendency that the foreign particles are produced at the area where an etching process is not performed after dry cleaning and the foreign particles deposited increase exponentially as an accumulated thickness of formed film becomes large.
It is described that a cleaning time can be estimated by measuring a change of a thickness of impurities deposited on a plate in a process chamber in Patent Document 4.
[Patent Document 1]
JP Patent Kokai Publication No. JP-P2005-535130A
[Patent Document 2]
International Laid-Open No. WO99/24640
[Patent Document 3]
JP Patent Kokai Publication No. JP-H06-188223A
[Patent Document 4]
JP Patent Kokai Publication No. JP-H11-176714A
[Non-Patent Document 1]
T. Moriya, M. Shimada and K. Okuyama; “Reduction of particles in plasma etching device—Monitoring of particles and inhibition of production of particles in etching device”, Clean Technology (February, 2006).
[Non-Patent Document 2]
N. Ito, et. al.; “Reduction of particles-contamination in plasma etching equipment by dehydration of chamber wall”, Proceedings of Related Applied Physics Associated Meeting, 26a-D-2 (September, 2002).
[Non-Patent Document 3]
S. Sato, A. Tsukune, T. Goto; “Visualization of backflow particles from turbo molecular pump—Are particles in lower chamber really recoiled?”, Clean Technology (June, 2003).